Cliff's Quadrajet Parts and Rebuild Kits
General Category => Quadrajet Carb Talk and Tips => Topic started by: Frank400 on January 08, 2014, 05:24:55 PM
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Am I right assuming that when you're on fast idle (choke flapped closed or partially closed, cold morning) and your vacuum advance runs off ported vacuum, then a lot more initial timing is part of the equation when engine is cold ?
Frank.
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basically yes but it depends on how far your throttle is open with the choke on and at what point the canister in the advance opens but basically the throttle is open far enough to send a vac signal to the ported vac source. then you have to take into account at what rpm you are at with the choke on as far as mechanical advance is concerned. so full advance, probably not but a lot more advance than at a regular warm idle. on top of that with the choke flap closed, that in itself causes the vacuum to rise on the top side of the throttle plates. some times the A/F ratio on the choke can be as low as 2:1. Really pig rich, that requires more advance. One thing that helps is the heat riser valve that causes a small portion of the fuel to be vaporized which helps. The good thing about the Qjet is with the dual boosters, the warm up process is more efficient.